Salt glazing is an old technique in pottery that is becoming a new craze for collectors. It originated in the Rhineland region of Germany between the 13th and 14th centuries but has evolved and developed greatly, making it unique and unpredictable pottery. Collectors love the beautiful results of salt glazing. As stoneware pottery, it is more difficult to find, making it more appealing to hobbyists.
What is salt glazing?
Salt glazing uses a unique method of applying the glaze. Instead of applying a coat of glazing minerals before firing, potters completely cover pots in sodium vapours and fire. The salt is added to the kiln at 200 degrees and releases sodium that acts as a flux of silica. The vapours then melt the surface; that is why it is also called vapour glazing. The discovery of this process came from the use of salt soaked wood from barrels that contained brined food.
The salt creates vapours that react with clay at a very high temperature, or with the silica, and produces sodium silicate. The latter is liquid glass, so it naturally glazes the pot with the clay’s properties. Classic pots made using this method have a distinct orange peel look, but potters would later realise that adding salt when firing can create various effects.
As an alternative to salt glazing, soda glazing was developed as it is less toxic. The technique is the same, and both salt and soda create sodium vapour. Soda produces sodium carbonate, which has no chloride.
How is it done?
Wares should first be bisque fired before salt glazing. Salt is thrown carefully into the kiln’s firebox with a steel angle at a temperature of about 1300 degree Celsius. It should vaporize before hitting the floor. Some potters add sodium carbonate to water and spray it. To achieve the orange peel look, add a pound of salt for every cubic foot of kiln. When the vapours start to form, they will start dropping on the pot. Those drops identify salt glazing. Most potters use separate kilns for salt glazing because residue can build up inside, which may have an effect on other firings.
Salt glazing achieves texture, surface and colour quality that no other process can. Each is unique, which is challenging yet remarkable in a market of uniformity and mass production. Firings can affect any slip or underglaze on pots and result in interesting, varied outcomes. No doubt, this technique adds brilliant texture from building up the layers to the marking of salt vapours. No wonder famous potters such as Bernard Leach embraced it. His works are displayed in London’s Victoria and Albert Museum.
Salt glazing is a difficult, yet addictive process, as potters would put it. Today, it is practised by a dedicated few. It involves science, as you have to put salt at the right temperature. As an art, it takes a great deal of skill to throw salt. Beginners may take two years to learn it. In the UK, there is only one company licensed to produce salt glazed pottery.
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